An aircraft manufacturer's chief executive and mechanic have been identified as the victims in Tuesday's fatal plane crash in Oshkosh.

Jeremy T. Monnett, 40, the CEO of Sonex, and Michael J. Clark, 20, an assembly mechanic at the company, were killed when a Sonex plane crashed shortly before 3:30 p.m. Tuesday near Wittman Regional Airport.

"It is with heavy hearts that we report the loss of two members of our Sonex family," the company posted on its website Wednesday.

Sonex, which is based in Oshkosh, is a manufacturer of experimental kit aircrafts. It was founded by John Monnett, Jeremy's father.

Oshkosh police confirmed Wednesday that Jeremy Monnett and Clark were killed when the plane they were in crashed on the back parking lot of Oshkosh Corp., which is near the airport. Police said both men died at the scene.

The Federal Aviation Administration and National Transportation Safety Board are investigating the cause of the crash, police said.

The plane is two-passenger Sonex SA fixed-wing, single-engine aircraft that is sold as a kit.

Known for its canary yellow planes, Sonex has been an exhibitor at EAA AirVenture in Oshkosh for years, located in the homebuilders area of the sprawling aviation convention at Wittman Regional Airport, a short distance from where Monnett's plane crashed.

The Experimental Aircraft Asociation (EAA) was started by home-built plane enthusiasts. Sonex sells complete plane kits for builders to assemble at a fraction of the cost of factory-built single-engine planes.

The company has been an innovator in the push for electric planes. In 2007 Sonex unveiled its eFlight technology to power one of its Waiex kit planes with an electric motor and batteries, first flown in 2010.

Dick Knapinski, a spokesman for EAA, said he has known Jeremy Monnett for 15 years and described him as an irreplaceable member of not only the sport aviation world but also the Oshkosh community.

"I don't think it's possible to overestimate his influence, even at a relatively young age," Knapinski said.

He described Sonex as one of the top five leading aircraft kit manufacturers in the world, and said the company's success and reputation have won it a large fan base. The company said the plane, a Sonex Sport Acro, has been "flawless in all respects."